Weighted Rope Crunch
Kneel in front of a high cable stack with a rope attachment. Hold the rope with your hands on either side of your head. Crunch forward while bringing your elbows toward your stomach.

Hanging Leg Lift
Grab a chin-up bar and hang your body off the ground. Without rocking or swinging, raise your straight legs as high as you can.

45-degree Laying Windshield Wiper
Lay on your back with your arms out to your sides. Bring your legs straight up until you have a 90-degree angle at your hips. With control sweep your legs from side to side, achieving a 45-degree angle with the floor.